Liquid crystal display device having improved cooling efficiency

ABSTRACT

A liquid crystal display device includes a liquid crystal display panel, a light guide plate disposed on a lower part of the liquid crystal display panel, an LED circuit substrate disposed along at least one side of the light guide plate to accommodate an LED on a front surface thereof, and a heat transmission member having a first part that faces a lower surface of the light guide plate and a second part that is extendedly bent from the first part and faces the LED circuit substrate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of prior application Ser. No. 14/538,053 filedNov. 11, 2014, which is a continuation of prior application Ser. No.14/253,456 filed Apr. 15, 2014, which is a continuation of priorapplication Ser. No. 11/450,373, filed on Jun. 12, 2006 in the U.S.Patent and Trademark Office, which claims priority under 35 U.S.C. §119(a) from Korean Patent Application No. 10-2005-0050440, filed on Jun.13, 2005, in the Korean Intellectual Property Office, the disclosures ofwhich are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present general inventive concept relates to a liquid crystaldisplay, and more particularly, to a liquid crystal display having alight emitting diode (LED) as a light source.

2. Description of the Related Art

Recently, flat panel displays, such as a liquid crystal display (LCD), aplasma display panel (PDP), or an organic light emitting diode (OLED),have been widely developed to replace a conventional cathode ray tube(CRT).

The LCD comprises a liquid crystal display panel, which has a thin filmtransistor substrate, a color filter substrate, and liquid crystalinterposed between the thin film transistor substrate and the colorfilter substrate. Since the LCD is a non-light emitting apparatus, theLCD needs a backlight unit, which is disposed on a rear surface of thethin film transistor substrate, to supply light to the liquid crystaldisplay panel. The amount of transmission of the light emitted from thebacklight unit is controlled according to an array state of the liquidcrystal. The LCD panel and the backlight unit are accommodated in achassis.

The backlight unit can be classified as one of an edge type backlightand a direct type backlight according to a position of a light source.The edge type backlight has a structure in which the light source isdisposed on a lateral part of a light guide plate. The edge typebacklight is applied to a relatively small liquid crystal display, whichis generally used in laptop and desktop computers. The edge typebacklight is advantageous for having high uniformity of luminance, longlifetime, and thin thickness.

A light emitting diode (LED) has been widely used as the light source ofthe backlight unit due to its high brightness and excellent colorrealization. However, the LED generates much heat compared to otherlight sources, such as a cold cathode fluorescent lamp (CCFL) or anexternal electrode fluorescent lamp (EEFL). The heat from the LED maylower brightness and cause color shifts if it is not properlydischarged.

Conventional backlight units use a radiating fin, a heat pipe, and acooling fan to remove heat generated by the LED, thereby making the LCDheavier and thicker.

SUMMARY OF THE INVENTION

The present general inventive concept provides a liquid crystal display(LCD) that has a thin thickness and an excellent LED cooling efficiency.

Additional aspects and/or advantages of the present general inventiveconcept will be set forth in part in the description which follows and,in part, will be obvious from the description, or may be learned bypractice of the present general inventive concept.

The foregoing and/or other aspects and utilities of the present generalinventive concept can be achieved by providing a liquid crystal displaydevice, comprising a liquid crystal display panel, a light guide platedisposed on a lower part of the liquid crystal display panel, an LEDcircuit substrate disposed along at least one side of the light guideplate to accommodate an LED on a front surface of the LED circuitsubstrate, and a heat transmission member having a first part that facesa lower surface of the light guide plate and a second part whichextendedly bends from the first part and faces the LED circuitsubstrate.

The heat transmission member can comprise a first sub-layer formedacross the first part and the second part of the heat transmissionmember, and a second sub-layer provided on at least a part of anexternal surface of the first sub-layer.

The first sub-layer can be made of aluminum.

A heat transmission of the second sub-layer can be larger than a heattransmission of the first sub-layer.

The second sub-layer can be made of graphite.

At least a part of the second sub-layer can be provided in the secondpart of the heat transmission member.

The heat transmission of the second sub-layer can be greater than orequal to about 400 W/m².

The LED circuit substrate can be made of metal.

The liquid crystal display can further comprise a gap pad disposedbetween the LED circuit substrate and the heat transmission member.

The liquid crystal display can further comprise a reflection platedisposed at a rear side of the light guide plate, the reflection platecomprising a first surface disposed on a lower part of the light guideplate, a second surface extendedly bent from the first surface anddisposed between the light guide plate and the LED, and comprising anLED accommodating hole to accommodate the LED, and a third surfaceextended from the second surface parallel to the liquid crystal displaypanel to cover a part of the light guide plate.

The liquid crystal display can further comprise a reflection cover toreflect light from the LED toward the light guide plate and toaccommodate the LED circuit substrate.

The liquid crystal display can further comprise a first gap pad disposedbetween the LED circuit substrate and the reflection cover, and a secondgap pad disposed between the reflection cover and the heat transmissionmember.

The foregoing and/or other aspects and utilities of the present generalinventive concept can also be achieved by providing a liquid crystaldisplay unit, comprising a liquid crystal display panel, a first platelocated on a bottom surface of the liquid crystal display panel to guidelight to the liquid crystal display panel, a second plate located on abottom surface of the first plate to reflect light to the first plate, alight source substrate having at least one light source to provide thelight to the liquid crystal display panel through the first plate, and afirst member located on a bottom surface of the second plate andcontacting the light source substrate to transfer heat away from the atleast one light source.

The second plate can comprise a first surface parallel to the bottomsurface of the first plate, a second surface perpendicular to the firstsurface, and a third surface parallel to the first surface and separatedfrom the first surface by the second surface. The light source substratecan be located on the second surface of the second plate. The thirdsurface of the second plate can prevent light from the at least onelight source from reaching the liquid crystal display panel withoutpassing through the first plate. The second surface of the second platecan include at least one hole to accommodate the at least one lightsource of the light source substrate. The first member can comprise afirst surface parallel to the bottom surface of the first plate, and asecond surface perpendicular to the first surface and contacting thelight source substrate. The first member can further comprise at leastone additional surface perpendicular to the first surface. The liquidcrystal display unit can further comprise a second member located on asurface of the first member and contacting the first member to transferheat away from the at least one light source and the first member. Thesecond member can comprise at least one of a first surface parallel tothe bottom surface of the first plate, and a second surfaceperpendicular to the first surface and contacting the second surface ofthe first member.

The liquid crystal display panel can comprise a thin film transistorsubstrate, a color filter substrate, a sealant connecting the thin filmtransistor substrate and the color filter substrate, a closed spacehaving a boundary defined by the thin film transistor substrate, thecolor filter substrate, and the sealant, and a liquid crystal layerlocated in the closed space. The first member can indirectly contact thelight source substrate. The first member can indirectly contact thelight source substrate through a plurality of intervening parts. Theplurality of intervening parts can comprise a reflection part to reflectthe light from the at least one light source to the first plate, and aheat transfer part to transfer the heat from the at least one lightsource to the first member.

The light source substrate can contact the first plate. The at least onelight source can be located on a first surface of the light sourcesubstrate, and the first member can contact a second surface of thelight source substrate. A heat transmission of the second member can begreater than a heat transmission of the first member. The heattransmission of the first member can be in a range of about 150 W/m² toabout 400 W/m², and the heat transmission of the second member can begreater than or equal to about 400 W/m².

The foregoing and/or other aspects and utilities of the present generalinventive concept can also be achieved by providing a display device,comprising a panel, a guide unit disposed at a rear side of the panel toguide light to the panel, a light source disposed on an outer portion ofthe guide unit to emit the light to the guide unit, and a heat transfermember to create a heat transfer path to transfer heat from the lightsource to outside of the display device at a rear side thereof.

The heat transfer member can operate without a cooling fan. The heattransfer member can have a surface area that is greater than or equal toa surface area of the panel. The heat transfer member can be parallel tothe panel and can be exposed at a rear portion of the display device.The light source can be disposed at an edge of the guide unit. The heatmember can form the heat transfer path to transfer heat in a firstdirection from the light source to a side portion of the display deviceand in a second directed from the side portion of the display devicetoward a rear portion of the device.

The foregoing and/or other aspects and utilities of the present generalinventive concept can also be achieved by providing a display panelcasing, comprising a cover, a guide unit disposed at a rear portion ofthe cover, a light source disposed at an edge portion of the guide unit,and a heat transmission member comprising a rear panel of the casing andforming a path to transfer heat from the light source to the rear panel.The heat transfer member can comprise a first portion that is the rearpanel of the casing, and a second portion extending perpendicular to thefirst portion and extending between the cover and the guide unit toclosely contact the light source.

The foregoing and/or other aspects and utilities of the present generalinventive concept can also be achieved by providing a method of coolinga liquid crystal display apparatus, comprising transferring heatgenerated by a light source to a heat transfer member having a heattransmission of greater than or equal to 150 W/m², and transferring theheat from the heat transfer member to outside of the liquid crystaldisplay apparatus. The method can further comprise transferring the heatfrom the heat transfer member to a secondary heat transfer member, andtransferring the heat from the secondary heat transfer member to outsideof the liquid crystal display apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or other aspects and advantages of the present generalinventive concept will become apparent and more readily appreciated fromthe following description of the embodiments, taken in conjunction withthe accompany drawings of which:

FIG. 1 is an exploded perspective view illustrating a liquid crystaldisplay (LCD) device according to an embodiment of the present generalinventive concept;

FIG. 2 illustrates a sectional view of the LCD device of FIG. 1;

FIG. 3 illustrates a cooling flow of the LCD device of FIG. 1;

FIG. 4 is a sectional view illustrating main parts of a liquid crystaldisplay (LCD) device according to another embodiment of the presentgeneral inventive concept; and

FIG. 5 is a sectional view illustrating main parts of a liquid crystaldisplay (LCD) device according to still another embodiment of thepresent general inventive concept.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the embodiments of the presentgeneral inventive concept, examples of which are illustrated in theaccompanying drawings, wherein like reference numerals refer to likeelements throughout. The embodiments are described below in order toexplain the present general inventive concept by referring to thefigures.

A liquid crystal display (LCD) device according to an embodiment of thepresent general inventive concept will be described with reference toFIGS. 1 and 2.

FIG. 1 is an exploded perspective view illustrating the LCD deviceaccording to this embodiment of the present general inventive concept.FIG. 2 is a sectional view illustrating the LCD according to thisembodiment of the present general inventive concept.

A liquid crystal display (LCD) device 1 comprises a liquid crystaldisplay panel 20, a light control member 30 disposed on a rear surfaceof the liquid crystal display panel 20, a light guide plate 40 disposedon a rear surface of the light control member 30, a light emitting diode(LED) circuit substrate 51 disposed on an incident surface of the lightguide plate 40 to accommodate an LED 52, a reflection plate 60 disposedacross a reflection surface, the incident surface, and an emittingsurface of the light guide plate 40, a heat transmission member 70, andan auxiliary heat transmission member 80. The liquid crystal displaypanel 20, the light control member 30, and the light guide plate 40 areaccommodated between a cover 10 and the heat transmission member 70.

Referring to FIGS. 1 and 2, the liquid crystal display panel 20 maycomprise a thin film transistor substrate 21 that forms a thin filmtransistor on the liquid crystal display panel 20, a color filtersubstrate 22 to face the thin film transistor substrate 21, a sealant 23to bond the thin film transistor substrate 21 and the color filtersubstrate 22 and to form a cell gap, and a liquid crystal layer 24disposed between the thin film transistor substrate 21, the color filtersubstrate 22, and the sealant 23 in the cell gap. The liquid crystaldisplay panel 20 displays a picture by controlling an alignment ofliquid crystal molecules of the liquid crystal layer 24. As the liquidcrystal display panel 20 is a non-light emitting element, the liquidcrystal layer 24 receives light from the LED 52 of the LED circuitsubstrate 51. A driver 25 can be disposed on a first side of the thinfilm transistor substrate 21 to apply a driving signal. The driver 25can comprise a flexible printed circuit (FPC) substrate 26, a drivingchip 27 mounted in the FPC substrate 26, and a printed circuit board(PCB) 28 connected to a side of the FPC substrate 26. The driver 25illustrated in FIG. 1 is an example of a chip on film (COF) method toconfigure the driver 25. However, other known methods include a tapecarrier package (TCP), a chip on glass (COG), and the like to configurethe driver 25. Alternatively, the driver 25 may be mounted in the thinfilm transistor substrate 21 to form a wire.

The light control member 30 disposed on the rear surface of the liquidcrystal display panel 20 may comprise a diffusion film 31, a prism film32, and a protection film 33.

The diffusion film 31 may comprise a base board and a coating layerhaving bead shaped members formed on the base board. The heat from theLED 52 is converted into plane light by the light guide plate 40 and isdiffused by the diffusion film 31 to be uniformly supplied to the entireliquid crystal display panel 20.

The prism film 32 is formed with prisms, each of which are shaped like atriangular pillar and are disposed on an upper surface of the prism film32 at a predetermined interval. The prism film 32 concentrates lightdiffused by the diffusion film 31 in a vertical direction toward theliquid crystal display panel 20. The prism film 32 may comprise twosheets, and forms a predetermined angle with a micro prism formed in theprism film 32. A majority of light passing through the prism film 32passes vertically to produce a uniform brightness distribution. Areflection polarizing film (not illustrated) may be used together withthe prism film 32 as necessary or as desired. Alternatively, only thereflection polarizing film may be used, without the prism film 32.

The protection film 33 is disposed on a top portion of the light controlmember 30. The protection film 33 protects the prism film 32 fromscratching.

The light guide plate 40 disposed on the rear surface of the lightcontrol member 30 changes a path of light incident from the LED 52disposed on a lateral part of the light guide plate 40 to supply planelight to the light control member 30. The light guide plate 40 comprisesthe incident surface to receive the light from the LED 52, the emittingsurface to emit the light to the light control member 30, and thereflection surface to face the incident surface and to reflect somelight that is not initially directed toward the light control member 30.The reflection surface may form a prism pattern (not illustrated), aV-cut pattern (not illustrated), and a diffusion pattern (notillustrated). The light guide plate 40 can be made of, for example, atransparent acryl material. The light guide plate 40 illustrated inFIGS. 1 and 2 is a plate type light guide plate. Alternatively, a wedgetype light guide plate may be used.

The LED circuit substrate 51 is disposed along a first side (i.e., thelateral part) of the light guide plate 40.

The LED 52 is mounted in the LED circuit substrate 51 to face the lightguide plate 40. Each LED 52 of an array of LEDs mounted on the LEDcircuit substrate 51 may emit a red light, a blue light, or a greenlight to supply a white light to the liquid crystal display panel 20.The LED 52 and the light guide plate 40 are spaced at a predeterminedinterval to mix the respective lights. The heat generated by the LED 52is directly supplied to the LED circuit substrate 51. The LED circuitsubstrate 51 may be made of metal, such as aluminum having excellentheat transmission efficiency, to efficiently discharge heat to outsideof the LCD device 1.

The reflection plate 60 comprises a first surface 61 disposed on a lowerpart of the light guide plate 40, a second surface 62 which extendedlybends from the first surface 61 to be disposed between the light guideplate 40 and the LED 52 and to form an LED accommodating hole 64 on thesecond surface 62 to accommodate the LED 52, and a third surface 63which extends to be parallel to the liquid crystal display panel 20 fromthe second surface 62 and to cover a part of the light guide plate 40.

The first surface 61 sends light incident below from the reflectionsurface of the light guide plate 40 back to the light guide plate 40 toimprove light efficiency. The second surface 62 prevents light from theLED 52 from being incident on the LED circuit substrate 51 through theLED accommodating hole 64. A size of the LED accommodating hole 64 canbe similar to a size of the LED 52. The third surface 63 prevents lightfrom the LED 52 from being directly incident on the light control member30 without passing through the light guide plate 40. If light from theLED 52 does not pass through the light guide plate 40, a bright line mayoccur along a side part of a screen (not illustrated).

The reflection plate 60 may be made of, for example,polyethyleneterephthalate (PET) or polycabonate (PC).

The heat transmission member 70 accommodates the light guide plate 40,the LED 52, and the reflection plate 60. The heat transmission member 70comprises a lower surface 71 disposed on a rear surface of the lightguide plate 40, and a side surface 72 upwardly bent from the lowersurface 71.

The heat transmission member 70 transmits heat generated by the LED 52to outside of the LCD device 1. Thus, a part of the side surface 72 isin close contact with, or is closely adhered to, a rear surface of theLED circuit substrate 51. The heat transmission of the heat transmissionmember 70 can be about 150 W/m² or greater. For example, the heattransmission of the heat transmission member 70 can be in a range ofabout 150 W/m² to about 400 W/m², such as about 150 W/m² to about 300W/m². The heat transmission member 70 may be made of, for example,aluminum.

The auxiliary heat transmission member 80 is attached to an externalsurface of the heat transmission member 70. The auxiliary heattransmission member 80 comprises a lower surface 81 disposed on the rearsurface of the light guide plate 40 and a side surface 82 upwardly bentfrom the lower surface 81. The heat transmission of the auxiliary heattransmission member 80 can be larger than that of the heat transmissionmember 70. For example, the heat transmission of the auxiliary heattransmission member 80 can be about 400 W/m² or greater. Furthermore,the heat transmission of the auxiliary heat transmission member 80 maybe in a range of about 400 W/m² to about 1,000 W/m². The auxiliary heattransmission member 80 may be made of, for example, graphite, and thelike. Although the auxiliary heat transmission member 80 is disposed onboth the lower surface 71 and the side surface 72 of the heattransmission member 70 in this embodiment of the present generalinventive concept, the present general inventive concept is not solimited. Accordingly, in various embodiments of the present generalinventive concept, the auxiliary heat transmission member 80 maycomprise either the lower surface 81 or the side surface 82, as opposedto both of the lower surface 81 or the side surface 82.

The liquid crystal display 1 according to this embodiment of the presentgeneral inventive concept is smaller in size and better in LED coolingefficiency compared to a conventional liquid crystal display employing,for example, a radiating fin and/or a cooling fan. In fact, the liquidcrystal display device 1 does not need a radiating fin or a cooling fanin order to cool efficiently.

Hereinafter, the liquid crystal display device 1 according to theabove-described embodiment of the present general inventive concept willbe described in detail with reference to FIG. 3.

The LED 52 generates a large amount of heat while being driven. The heatfrom the LED 52 is transmitted to the LED circuit substrate 51. Sincethe LED circuit substrate 51 and the heat transmission member 70 are inclose contact with, or are closely adhered to, each other, the heatmoves to the heat transmission member 70. The heat transmitted to theheat transmission member 70 having high heat transmission passes throughthe side surface 72 of the heat transmission member 70 and the lowersurface 71 efficiently.

As the heat transmission member 70 contacts (e.g., is adhered to) theauxiliary heat transmission member 80, the heat from the heattransmission member 70 moves to the auxiliary heat transmission member80. The heat is efficiently transmitted to the lower surface 81 of theauxiliary heat transmission member 80 through the heat transmissionmember 70 as the heat transmission of the auxiliary heat transmissionmember 80 is larger than that of the heat transmission member 70.Furthermore, the heat is transmitted to the lower surface 81 of theauxiliary heat transmission member 80 to be quickly discharged to theoutside, since a surface area of the lower surface 81 in contact withexternal air is large.

Each LED 52 is a point light source, thereby forming a plurality of hotspots in the LED circuit substrate 51. However, the heat is distributedacross the auxiliary heat transmission member 80 by passing through theheat transmission member 70 and the auxiliary heat transmission member80. Since the auxiliary heat transmission member 80 has a larger surfacearea in contact with external air, the liquid crystal display device 1has a high LED cooling efficiency.

As described above, the LED 52 is efficiently cooled by the heattransmission member 70 and the auxiliary heat transmission member 80 inthis embodiment of the present general inventive concept, without usingconventional cooling devices, such as the radiating fin or the coolingfan. Accordingly, the liquid crystal display device 1 may be lighter,thinner and calmer as compared to a conventional LCD.

Hereinafter, a liquid crystal display according to another embodiment ofthe present general inventive concept will be described with referenceto FIG. 4.

As illustrated in FIG. 4, a liquid crystal display according to thisembodiment of the present general inventive concept comprises a gap pad91 disposed as an intervening part between an LED circuit substrate 51and a heat transmission member 70. The gap pad 91 is a thin plate madeof material having a high heat transfer coefficient, and can have athickness of, for example, approximately 0.5 mm.

The LED circuit substrate 51 and the heat transmission member 70 may bemade of metal having high heat transmission efficiency. Even though theLED circuit substrate 51 and the heat transmission member 70 are inclose contact with, or are closely adhered to, each other, a hollow areais generated between the LED circuit substrate 51 and the heattransmission member 70 that lowers heat transmission efficiency. The gappad 91 is in close contact with, or is closely adhered to, both the LEDcircuit substrate 51 and the heat transmission member 70, which are madeof metal, to improve heat radiation efficiency. Heat from an LED 52sequentially passes through the LED circuit substrate 51, the gap pad91, and the heat transmission member 70 to be transmitted to anauxiliary heat transmission member 80.

Hereinafter, a liquid crystal display according to still anotherembodiment of the present general inventive concept will be describedwith reference to FIG. 5.

As illustrated in FIG. 5, a liquid crystal display according to thisembodiment of the present general inventive concept comprises asimplified reflection plate 65. The liquid crystal display according tothis embodiment further comprises a reflection cover 53 to cover an LEDcircuit substrate 51. Unlike in FIGS. 1-3, the reflection plate 65according to this embodiment is disposed on a lower part of a lightguide plate 40 alone (e.g., without being connected to the LED circuitsubstrate 51 or an LED 52). The reflection cover 53 reflects light fromthe LED 52 toward the light guide plate 40. The reflection cover 53 maybe made of highly reflection-efficient metal. Gap pads 92 and 93 aredisposed between the reflection cover 53 and the LED circuit substrate51, and disposed between the reflection cover 53 and a heat transmissionmember 70, respectively. Heat from the LED 52 sequentially passesthrough the LED circuit substrate 51, the gap pad 92, the reflectioncover 53, the gap pad 93, and the heat transmission member 70 to betransmitted to an auxiliary heat transmission member 80. The gap pads 92and 93 and the reflection cover 53 are intervening parts disposedbetween the LED circuit substrate 51 and the heat transmission member70.

Although the embodiments described above illustrate the heattransmission member 70 and the auxiliary heat transmission member 80 inthe absence of conventional cooling devices, the present generalinventive concept is not so limited. Accordingly, in various embodimentsof the present general inventive concept, a heat transmission member andan auxiliary heat transmission member may be used together with one ormore conventional cooling devices, such as a radiating fin, a heat pipe,a cooling fan, and an aluminum radiating plate, to improve LED coolingefficiency. Furthermore, although FIGS. 1-5 illustrate two distinct heattransmission members (i.e., the heat transmission member 70 and theauxiliary heat transmission member 80), the liquid crystal displaydevice according to various embodiments of the present general inventiveconcept may include a single heat transmission member that includes aplurality of sub-layers. For example, the liquid crystal display devicemay include a single heat transmission member containing a firstsub-layer (e.g., corresponding to the heat transmission member 70), anda second sub-layer (e.g., corresponding to the auxiliary heattransmission member 80).

Although a few embodiments of the present general inventive concept havebeen shown and described, it will be appreciated by those skilled in theart that changes may be made in these embodiments without departing fromthe principles and spirit of the general inventive concept, the scope ofwhich is defined in the appended claims and their equivalents.

What is claimed is:
 1. A backlight unit, comprising: a light guideelement arranged parallel with a liquid crystal display panel; a circuitsubstrate including a metallic substrate and arranged with the lightguide element, a front surface of the circuit substrate facing a lateralside of the light guide element; light emitting diodes (LEDs) arrangedon the front surface of the circuit substrate to emit light toward thelateral side of the light guide element; a first heat transmissionmember having a first portion arranged along the light guide element, aninner surface of the first portion of the first heat transmission memberfacing a bottom surface of the light guide element, and a second portionextending from an end of the first portion of the first heattransmission member to be arranged along the circuit substrate, an innersurface of the second portion of the first heat transmission memberfacing a rear surface of the metallic substrate of the circuitsubstrate; a second heat transmission member having a first portionarranged along the first portion of the first heat transmission member,an outer surface of the first portion of the second heat transmissionmember contacting the inner surface of the first portion of the firstheat transmission member, and a second portion arranged along the secondportion of the first heat transmission member, an outer surface of thesecond portion of the second heat transmission member contacting theinner surface of the second portion of the first heat transmissionmember; an intervening element disposed between the circuit substrateand the second portion of the second heat transmission member, an innersurface of the intervening element contacting the rear surface of themetallic substrate of the circuit substrate and an outer surface of theintervening element contacting an inner surface of the second portion ofthe second heat transmission member; and a reflection element disposedbetween the light guide element and the first portion of the second heattransmission member, an upper surface of the reflection elementcontacting the bottom surface of the light guide element and a bottomsurface of the reflection element contacting an inner surface of thefirst portion of the second heat transmission member to reflect thelight toward the liquid crystal display panel through the light guideelement, wherein the LEDs are arranged to be spaced apart from thelateral side of the light guide element.
 2. The backlight unit of claim1, wherein the first second heat transmission member is in thermalcontact with the LEDs and the circuit substrate to receive heat from theLEDs through the circuit substrate and transmit the received heat to thefirst heat transmission member.
 3. The backlight unit of claim 1,wherein the intervening element includes a gap pad which has a thinplate shape.
 4. The backlight unit of claim 1, wherein the inner surfaceand the outer surface of the intervening element adhere the rear surfaceof the metallic substrate of the circuit substrate and the inner surfaceof the second portion of the second heat transmission member,respectively, and wherein the intervening element is in thermal contactwith the circuit substrate and the second heat transmission member. 5.The backlight unit of claim 1, wherein a size of the upper surface ofthe reflection element is larger than a size of the bottom surface ofthe light guide element.
 6. The backlight unit of claim 1, wherein thefirst heat transmission member and the second heat transmission memberare made of graphite and metal, respectively.
 7. A display device,comprising: a liquid crystal display panel; and a back light unit,wherein the back light unit comprises: a light guide element arrangedparallel with the liquid crystal display panel; a circuit substrateincluding a metallic substrate and arranged with the light guideelement, a front surface of the circuit substrate facing a lateral sideof the light guide element; light emitting diodes (LEDs) arranged on thefront surface of the circuit substrate to emit light toward the lateralside of the light guide element; a first heat transmission member havinga first portion arranged along the light guide element, an inner surfaceof the first portion of the first heat transmission member facing abottom surface of the light guide element, and a second portionextending from an end of the first portion of the first heattransmission member to be arranged along the circuit substrate, an innersurface of the second portion of the first heat transmission memberfacing a rear surface of the metallic substrate of the circuitsubstrate; a second heat transmission member having a first portionarranged along the first portion of the first heat transmission member,an outer surface of the first portion of the second heat transmissionmember contacting the inner surface of the first portion of the firstheat transmission member, and a second portion arranged along the secondportion of the first heat transmission member, an outer surface of thesecond portion of the second heat transmission member contacting theinner surface of the second portion of the first heat transmissionmember; an intervening element disposed between the circuit substrateand the second portion of the second heat transmission member, an innersurface of the intervening element contacting the rear surface of themetallic substrate of the circuit substrate and an outer surface of theintervening element contacting an inner surface of the second portion ofthe second heat transmission member; and a reflection element disposedbetween the light guide element and the first portion of the second heattransmission member, an upper surface of the reflection elementcontacting the bottom surface of the light guide element and a bottomsurface of the reflection element contacting an inner surface of thefirst portion of the second heat transmission member to reflect thelight toward the liquid crystal display panel through the light guideelement, wherein the LEDs are arranged to be spaced apart from thelateral side of the light guide element.
 8. The backlight unit of claim1, wherein the circuit substrate has a thin plate shape.
 9. Thebacklight unit of claim 1, wherein the inner surface of the firstportion of the second heat transmission member does not directly contactthe bottom surface of the light guide element.
 10. The backlight unit ofclaim 9, wherein the inner surface of the first portion of the firstheat transmission member does not directly contact the bottom surface ofthe light guide element.
 11. The backlight unit of claim 1, wherein thefirst portion of the second heat transmission member entirely extendsacross the bottom surface of the reflection element.
 12. The backlightunit of claim 1, wherein the reflection element has a portion whichextends toward the circuit substrate beyond the lateral side of thelight guide element.
 13. The backlight unit of claim 1, wherein the LEDsand the lateral side of the light guide element are spaced at apredetermined interval to mix the lights.
 14. The backlight unit ofclaim 13, wherein the reflection element has: a first portion on whichthe upper surface of the reflection element contacting the bottomsurface of the light guide element and the bottom surface of thereflection element contacting the inner surface of the first portion ofthe second heat transmission member are provided, a second portionextending from an end of the first portion of the reflection element tobe arranged along the circuit substrate, wherein holes are provided onthe second portion of the reflection element to accommodate the LEDs tobe spaced from the lateral side of the light guide element, and a thirdportion extending from an end of the second portion of the reflectionelement toward the lateral side of the light guide element.
 15. Thedisplay device of claim 7, wherein the second heat transmission memberis in thermal contact with the LEDs and the circuit substrate to receiveheat from the LEDs through the circuit substrate and transmit thereceived heat to the first heat transmission member.
 16. The displaydevice of claim 7, wherein the intervening element comprises a gap padwhich has a thin plate shape.
 17. The display device of claim 7, whereinthe inner surface and the outer surface of the intervening elementadhere the rear surface of the metallic substrate of the circuitsubstrate and the inner surface of the second portion of the second heattransmission member, respectively, and wherein the intervening elementis in thermal contact with the circuit substrate and the second heattransmission member.
 18. The display device of claim 7, wherein a sizeof the upper surface of the reflection element is larger than a size ofthe bottom surface of the light guide element.
 19. The display device ofclaim 7, wherein the first heat transmission member and the second heattransmission member are made of graphite and metal, respectively. 20.The display device of claim 7, wherein the circuit substrate has a thinplate shape.
 21. The display device of claim 7, wherein the innersurface of the first portion of the second heat transmission member doesnot directly contact the bottom surface of the light guide element. 22.The display device of claim 21, wherein the inner surface of the firstportion of the first heat transmission member does not directly contactthe bottom surface of the light guide element.
 23. The display device ofclaim 7, wherein the first portion of the second heat transmissionmember entirely extends across the bottom surface of the reflectionelement.
 24. The display device of claim 7, wherein the reflectionelement has a portion which extends toward the circuit substrate beyondthe lateral side of the light guide element.
 25. The display device ofclaim 7, wherein the LEDs and the lateral side of the light guideelement are spaced at a predetermined interval to mix the lights. 26.The display device of claim 25, wherein the reflection element has: afirst portion on which the upper surface of the reflection elementcontacting the bottom surface of the light guide element and the bottomsurface of the reflection element contacting the inner surface of thefirst portion of the second heat transmission member are provided, asecond portion extending from an end of the first portion of thereflection element to be arranged along the circuit substrate, whereinholes are provided on the second portion of the reflection element toaccommodate the LEDs to be spaced from the lateral side of the lightguide element, and a third portion extending from an end of the secondportion of the reflection element toward the lateral side of the lightguide element.
 27. A display device, comprising: a liquid crystaldisplay panel; and a back light unit, wherein the back light unitcomprises: a light guide element arranged parallel with the liquidcrystal display panel; a circuit substrate arranged with the light guideelement, a front surface of the circuit substrate facing a lateral sideof the light guide element; light emitting diodes (LEDs) arranged on thefront surface of the circuit substrate to emit light toward the lateralside of the light guide element; a first heat transmission member havinga first portion arranged along the light guide element, an inner surfaceof the first portion of the first heat transmission member facing abottom surface of the light guide element, and a second portionextending from an end of the first portion of the first heattransmission member to be arranged along the circuit substrate, an innersurface of the second portion of the first heat transmission memberfacing a rear surface of the metallic substrate of the circuitsubstrate; a second heat transmission member having a first portionarranged along the first portion of the first heat transmission member,an outer surface of the first portion of the second heat transmissionmember contacting the inner surface of the first portion of the firstheat transmission member, and a second portion arranged along the secondportion of the first heat transmission member, an outer surface of thesecond portion of the second heat transmission member contacting theinner surface of the second portion of the first heat transmissionmember; and a reflection element disposed between the light guideelement and the first portion of the second heat transmission member, anupper surface of the reflection element contacting the bottom surface ofthe light guide element and a bottom surface of the reflection elementcontacting an inner surface of the first portion of the second heattransmission member to reflect the light toward the liquid crystaldisplay panel through the light guide element, and wherein the LEDs arearranged to be spaced apart from the lateral side of the light guideelement.
 28. The display device of claim 27, wherein the second heattransmission member is in thermal contact with the LEDs and the circuitsubstrate to receive heat from the LEDs through the circuit substrateand transmit the received heat to the first heat transmission member.29. The display device of claim 27, wherein a size of the upper surfaceof the reflection element is larger than a size of the bottom surface ofthe light guide element.
 30. The display device of claim 27, wherein thecircuit substrate includes a metallic substrate which has a thin plateshape.
 31. The display device of claim 27, further comprising a gap padwhich has a thin plate shape and is disposed in contact between thecircuit substrate and the second portion of the second heat transmissionmember.
 32. The display device of claim 27, wherein the inner surface ofthe first portion of the second heat transmission member and the innersurface of the first portion of the first heat transmission member donot directly contact the bottom surface of the light guide element. 33.The display device of claim 27, wherein the first portion of the secondheat transmission member entirely extends across the bottom surface ofthe reflection element.
 34. The display device of claim 27, wherein theLEDs and the lateral side of the light guide element are spaced at apredetermined interval to mix the lights.
 35. The display device ofclaim 34, wherein the reflection element has: a first portion on whichthe upper surface of the reflection element contacting the bottomsurface of the light guide element and the bottom surface of thereflection element contacting the inner surface of the first portion ofthe second heat transmission member are provided, a second portionextending from an end of the first portion of the reflection element tobe arranged along the circuit substrate, wherein holes are provided onthe second portion of the reflection element to accommodate the LEDs tobe spaced from the lateral side of the light guide element, and a thirdportion extending from an end of the second portion of the reflectionelement toward the lateral side of the light guide element.
 36. Thebacklight unit of claim 1, wherein an air gap is provided between theLEDs and the lateral side of the light guide element.
 37. The displaydevice of claim 7, wherein an air gap is provided between the LEDs andthe lateral side of the light guide element.
 38. The display device ofclaim 27, wherein an air gap is provided between the LEDs and thelateral side of the light guide element.